Electric discharge device



June 18, 1940. Kq $|EBERTZ f 2,204,999

ELECTRIC DISCHARGE DEVICE Filed Dec. 8, 1937 //V VEN TR KARL S/EBERTZ ATTORNE Y lPatented June 18, 1940 UNITED STATES PATENT OFFICE ELECTRICDISCHARGE kDEVICE poration of Germany Application December 8,

1937, Serial No. 178,650

In Germany November 30, 1936 7 Claims.

This invention relates to electric discharge devices in which electriccurrents according to the principle of the electron multiplication areamplied in various steps by the secondary electrons. In this case it isimmaterial whether the currents to be amplified are released as photocurrents by the exposure of a photo-electric surface or whether theelectrons supplied by an electron emitting source, for instance, a hotcathode are influencedv by any control means, for instance, by theelectrostatic or electromagnetic control. The electron multipliershitherto known present a relatively elongated construction which givesrise to a number of diliculties in the manufacture of such devices.

These diiculties may be removed if the electrodes of the electronmultiplier are arranged in the form of a circular arc. In this manner itis possible to place on the one hand a large number of steps in arelatively narrow space and on the other hand the substances forpreparing the active surfaces of the electrodes of the multiplier may becentrally'arranged so that for the preparation of these layers allelectrodes are under the same conditions and, therefore, there is nogreat diiculty in giving the same emissive power to the electrodes ofthe individual steps that emit secondary electrons. It is also possibleto provide for a uniform heating of the electrodes when degassing andactivating. The arrangement of the electrodes in the form of a circulararc may be employed for purely electrostatically operating apparatus;however, particularly also' for apparatus in which the releasedsecondary electrons are deflected by means of magnetic fields towardsthe next following electrode. Sucharrangements have the furtheradvantage that the necessary magnetic field may be produced with the aidof a relatively small and simply constructed coil.

An embodiment of the invention is shown in the accompanying drawing foran electron multiplier operating with magnetic deflection.

Fig. 1 shows the plan view, Fig. 2 the elevational view of the electronmultiplierin diagrammatic form, Fig. 3 shows in detail one of thesecondary emissive surfaces, while Fig. l shows in somewhat more detaila portion of the sensitizing apparatus.

I denotes the vacuum vessel in which are sen cured the layers 2, forinstance, or mica serving to secure the individual electrodes. Theelectrodes which emit secondary electrons (main electrodes) are denotedby the numeral 3. They are supported by the rods 4 secured to the micalayers. The effective surface of the electrode itself projects towardsthe center of the discharge device as will be seen from Fig. 3 in whichan electrode is shown on an enlarged scale. This construction has thepurpose to prevent asv far as possible non-uniform iields which may becreated by holding wires 4. Within the circle on which the electrodes 3are arranged are disposed the acceleration electrodes 5 which are keptin a known manner at a suitable voltage. In the central portion of thedischarge device are arranged the substances for the preparation of anactive surface of the electrodes 3. In most cases it is sufficient toplace only the metal serving to directly activate the surface, such as,for instance, an alkali metal, for instance, caesium or an alkalineearth metal such as barium, in the central portion of the electricdischarge device in the form of known getter pills which are denoted bythe numeral I5 supported from the central support member 2 I. In orderto produce a uniform deposit on all electrodes various of such pills areprovided facing the single sections of the electrodes. A uniformimpinging of the vapor on the electrode surfaces may be attained in astill more certain manner if the vapor of the active metal is caused toissue from a circular gap or a portion of a circular gap. Such a gap maybe, for instance, obtained if the getter is placed in a pot 6 as shownin Fig. 4, a covering plate l being arranged in spaced relation thereto.The circular gap may be covered opposite to the portions of the potwalls which are not to be provided with a deposit in order to leave, forinstance, an aperture free for the passage of the light. Such a cover isdenoted in Fig. 4 by the numeral 8. The material evaporated inside thepot li leaves the same substantially in the direction as indicated bythe arrows. A similar construction may be employed in order, forinstance, to provide the electrodes 3 with a silver coating previous tothe impinging of the active material thereon, which silver coating maybe subsequently oxidized in a well known manner.` In this case thesilver to be evaporated is preferebly heated with the aid of a tungstenspiral, whereas the evaporation of the active material may be effectedby heating the container with the aid of high-frequency currents. Toprovide the electrodes with a silver coating also a tungsten wireprovided with a silver coating may be preferably arranged inside thespace enclosed by the acceleration electrodes 5 and opposite to theelectrodes 3.

It is preferable to arrange that the vapors serving to activate theelectrode Yare directed by guide surfaces towards those electrodes. Tothis end, the disks 9 and l0 are employed between which lies the activematerial. These disks may consist of metal and may serve at the sametime in the case of high-frequency heating to supply to the active metalthe heat necessary for its evaporation. It is advisable to provide stillfurther surfaces l l consisting preferably of insulating material forinstance, mica which surfaces may be, for instance, secured to theacceleration electrodes 5. A portion of the circular gap formed by thedisks il and l0 is covered preferably by the strip l2 as will be seenfrom Fig. l in order to maintain an aperture free for the passage of thelight when employing the device for the amplification of photo-currents.If the individual electrodes are impressed in a known manner with asuitable voltage in the clockwise direction so that the electrodedenoted by 3a represents, for instance, the input electrode, care mustbe taken that this electrode be struck by the luminous rays which are torelease the photoelectrons. If the device is to be employed to amplifythe currents supplied by a hot cathode and influenced by a control gridor the like, the input system consisting of the hot cathode and thecontrol electrode must be so arranged that the electrons emittedtherefrom impinge upon the input electrode. In the majority of casesthis is made possible by arranging the system consisting of the hotcathode and the control electrode in the same manner as the electrodes3. Such a cathode 3| and control electrode 33 are shown in Fig. l. inthis system one of the rods 5 or the electrode 3a may serve as an anode.The supply leads to the individual electrodes are shown only in part forclearness of illustration. The coil 23 serves to produce the magneticdeflecting iield and surrounds the envelope.

The above-described construction of the electron multiplier isparticularly employed in such cases where substances which evaporate ina relatively diilcult manner, such as barium, are utilized to activatethe individual electrode surfaces. Such substances are chiefly employedin apparatus in which the electron multiplier is utilized to control thecurrents produced by a hot cathode and influenced by grids or the likeand in which the active layer of the hot cathode contains alkaline earthmetals, such as barium or strontium. In this case the use of caesium orother alkali metals is under circumstances disadvantageous, since, forinstance, evaporating alkaline earth metal deteriorates the layersactive as secondary electron emitting sources or it deposits on theelectrodes of the incandescent electron arrangement.

What is claimed is:

l.. A discharge device comprising an elongated symmetrical tubularenvelope, an elongated cylindrical support member having its axiscoincident with the axis of the envelope, a plurality of equi-spacedcylindrical accelerating electrodes disposed concentrically about thesupport member and a plurality of individual secondary emissiveelectrodes concentric with said accelerating electrodes, a plurality ofsupport rods supporting each one of the plurality of secondary emissiveelectrodes, and spacing means maintaining the supported secondaryemissive electrodes in spaced relationship to each other and to both thesupport member and accelerating electrodes.

2. A discharge device comprising an elongated symmetrical tubularenvelope, an elongated cylindrical support member having its axiscoincident with the axis of the envelope, a plurality of equi-spacedcylindrical accelerating electrodes disposed concentrically about thesupport member, a plurality of individual secondary emissive electrodesconcentric with said accelerating electrodes, a cathode, a plurality ofsupport rods supporting each one of the plurality of secondary emissiveelectrodes, spacing means maintaining the supported secondary emissiveelectrodes in spaced relationship to each other and to both the supportmember and accelera-ting electrodes and maintaining the secondaryemissive electrodes equi-distantly spaced from each other, said cathodebeing positioned at a radial distance substantially equal to that ofsaid concentric secondary emissive electrodes.

3. A discharge device comprising an elongated symmetrical tubularenvelope, an elongated cylindrical support member having its axiscoincident with the axis of the envelope, a plurality of equi-spacedcylindrical accelerating electrodes disposed concentrically about thesupport member, a plurality of individual secondary emissive electrodesconcentric With said accelerating electrodes, a plurality of supportrods supporting each one of the plurality of secondary emissiveelectrodes, spacing means maintaining the supported secondary emissiveelectrodes in spaced relationship to each other and to both the supportmember and accelerating electrodes, and

means supported from the support member for sensitizing the secondaryemissive electrodes.

4. An electron discharge device comprising an elongated cylindricalsupport member, a plurality of parallel cylindrical acceleratingelectrodes equi-spaced from each other and concentric with said supportmember, a plurality of secondary emissive electrodes equi-spaced fromeach other and concentric with said support member, and lying beyond theaccelerating electrodes, said secondary emissive electrodes having anarcuate surface facing the support member, and means supported from thesupport member for sensitizing the arcuate surface of the secondaryemissive electrodes.

5. An electron discharge device comprising an elongated cylindricalsupport member, a plurality of parallel cylindrical acceleratingelectrodes equi-spaced from each other and concentric with said supportmember, a plurality of secondary emissive electrodes equi-spaced fromeach other and concentric with said support member, and lying beyond theaccelerating electrodes, each of said secondary emissive electrodeshaving an arcuate surface facing the support member, said arcuatesurface subtending an angle substantially not greater than the anglesubtended by two adjacent accelerating electrodes, and means supportedfrom the support member for sensitizing the arcuate surface of thesecondary emissive electrodes.

6. An electron discharge device comprising an elongated cylindricalcathode, an elongated cylindrical support member, a plurality ofparallel cylindrical accelerating electrodes equi-spaced from each otherand concentric with said support member, a plurality of secondaryemissive electrodes equi-spaced from each other and concentric with saidsupport member, said secondary emissive electrodes being at the sameradial distance as said cathode and lying beyond the acceleratingelectrodes, each of said secondary emissive electrodes having an arcuatesurface facing the support member, said arcuate surface subtending anangle substantially not greater than the angle subtended by two adjacentaccelerating electrodes, and means supported from the support member forsensitizing the arcuate surface of the secondary einissive electrodes.

7. An electron discharge device comprising an elongated cylindricalsupport member, a plu ralty of parallel cylindrical accelerating electrodes mounted concentrically about said support member, a plurality ofequi-spaced secondary emissive electrodes mounted concentrically aboutthe accelerating electrodes, each of said plurality of secondary emissveelectrodes having the shape of a non-planar base prism, said non-planarbase prism being sensitized to provide highly secondary electronemission and each of said secondary emissive electrodes being supportedfrom the apex of the prism, and an envelope concentric withl andenclosing said support member, said accelerating electrodes, and saidsecondary @missive electrodes.

KARL SIEBERTZ.

